A worm dubbed Win32/Conficker.A is making the rounds on Windows machines, exploiting a security hole that Microsoft released a patch for in October, Microsoft said on Wednesday.
The number of attacks have increased over the past couple of days, exploiting a critical vulnerability that was addressed by security update MS08-067.
"It opens a random port between port 1024 and 10000 and acts like a Web server. It propagates to random computers on the network by exploiting MS08-067. Once the remote computer is exploited, that computer will download a copy of the worm via HTTP using the random port opened by the worm. The worm often uses a .JPG extension when copied over and then it is saved to the local system folder as a random named dll," the posting said.
"It is also interesting to note that the worm patches the vulnerable API in memory so the machine will not be vulnerable anymore. It is not that the malware authors care so much about the computer as they want to make sure that other malware will not take it over too," Microsoft said.